If you are considering a yamaha, weight isn't a selling point. Being able to ride it year in and year out without any engine problems is why you buy a 4 stroke.
The yami owners have pretty much came to grips with the fact that we are riding the fat chick of sleds. There isn't anything wrong with that though, because we can shed some pounds, add a little boost and be the sexiest thing on the hill!
The three sleds you've asked about though, tkuss is pretty close, and I believe the RX1 is heavier than the apex, and is also carb'd instead of fuel injection.